Wouldn't surprise me at all if him and Lukaku had wanted out since Martinez last season, maybe even the middle of the second one. We were sliding down the table, no Moshiri millions, no hint of sacking RM and I think with Ross he believes he's taken the brunt of he crowds anger over the last two years of RM.
Barkley was sound for the first couple of months of RM last season, why didn't we open contract talks then? The team and him were then pretty dreadful until the end of that season, but we still could have negotiated with him without a manager. Maybe at that point the club were beginning to suspect he wasn't going to fulfill his potential and weren't willing to match the wages he wanted. Most of his performances over the last two years of RM wouldn't have warranted the kinds of wages he's been rumoured to be asking for.
Or, during the turmoil of the final few months of RM, with Stones wanting out, Lukaku wanting out, "they're not booing you ross" etc, maybe he thought that leaving was his best option. Spurs have gotten into his ear, Levy sensing he can get a bargain.
I don't think Koeman is particularly the reason he wants to leave but it makes a handy excuse for it. Don't forget Koeman made him captain in an early cup game, Barkley started most of our games, and when he was benched it was generally after an awful performance.